Insulation liner for motor core slots



1950 w. T. KIRKPATRICK 2,495,010

INSULATION LINER FOR MOTOR CORE SLOTS Filed Oct. 18, 1946 I N V EN TOR. Will iamZ- Kirkpatrick ATTORNEY Patented Jan. 17, 1950 INSULATION LINER FOB MOTOR CORE SLOTS William T. Kirkpatrick, North Plainfleld, N. 1.,

assignor to The Hoover Company, North Canton, Ohio, a corporation of Ohio Application October 18, 1948, Serial No. 704,017

8 Claims.

This invention relates to electric motors and more particularly to insulation liners for the core slots thereof together with the method of making the same.

In motors which have coil receiving slots spaced circumferentially about the core with the windings turned transversely of the slot edges so as to enter a slot circumferentially spaced from the first slot, the windings must make a comparatively short bend across the sharp edges of the ends of the core.

In many cases the coils are made of magnet wire which is insulated by an enamel film. If too great a stress is applied to the wire where it bends sharply across the sharp edges of the slots, the enamel film is sometimes broken resulting in a short-circuited winding which of necessity puts the motor out of operation and requires rewinding to put it back into operation.

In prior motors, an attempt has been made to solve this problem by providing insulation liners for the coil slots which extend beyond the ends of the core and are folded backwardly in a hemlike fold away from the slot towards the ends of the core so that a double ply of the liner supports the windings where they turn crosswise of the end edges of the slots.

This has not been entirely satisfactory because a single layer of the slot liner is still bent across the sharp edges of the slots which will eventually break the liner at that point and expose the magnet wire coils to the sharp edges of the slots.

According to the present invention, a reenforcement is provided for the insulating liner at the ends where the coils form the liner across the sharp edges at the ends of the slots. A strip of material having high dielectric and mechanical strength is cemented to the insulation liner beneath the overlapped folded seams and extends beyond the ends of the folds into the slot a short distance preferably, at least equal to the width of the fold.

More specifically, according to this invention, a slot liner is provided which is of rectangular formation before being assembled into the slots. Parallel edges are folded over into a hem-like formation with the ends of the folds facing each other so that the distance between the facing edges of the fold just equal the depth (or length) of the core with which the liner is to be used. Under the folded edges, a reenforcement is provided which extends from beneath the folded edges to a distance preferably equal to or greater than the width of the told. This reenforcement extends approximately to the closed end of the 2 fold and consists of a material having both high dielectric and mechanical strength. The material of which the reenforcement is made is preferably cellulose. acetate or some other cellulose derivative such as cellulose fiber having the necessary properties.

The length of the liner along the fold is such that the liner will cover the entire periphery of the slots with enough additional material so that the liner may be folded over at each end to provide for clamping of the coils and liner in the slots by means of slot wedges.

More specifically, the length of the insulation liner along the folds is such that when the liner is bent into U-shape and inserted in the slots, one side of the U-shaped liner may be folded crosswise of the slot to lie against the coils and turned rearwardly again so as to present a double layer of insulation pressing against the coils. The other side of the U-shaped liner is also folded across the slot below the double fold of the first side and extended backwardly again across the slot so that both sides present four layers of insulation between the coils and the slot wedges. This forms an excellent backing for the wedges and provides sufiicient insulation between the wedges and the coils.

In its broadest aspect, the present invention consists in the provision of a reenforcement of high dielectric and mechanical strength bonded to the outside of the ends of the slot liner where the coils tend to force the liner against the sharp edges of the slots, whether the liners be made of laminated material or just a plain insulating material. The reenforcement is in the form of a cellulose or other tape having the necessary properties secured to the lining strip adjacent each edge and spaced from the edges of the strip so that the edges of the strip can be folded back over the tape. The tape is of such width that it extends from the closed end of the folds beyond their free ends so as to extend between the liner and core when assembled. The liner used in disclosing this invention and which has been used in practice is made up of a sheet of paper, treated or untreated, with a sheet of treated fabric bonded thereto. When assembled, the fabric is positioned next to the coils and the paper next to the walls of the slots.

The laminated sheet of paper and fabric is then cut into strips of a width equal to the length or depth of the core with which the liners are to be used plus enough material for folding each edge of the strip into a hem-like formation. Strips of cellulose acetate or other cellulose derivative, having a tacky surface, are 'placed on the paper side of the strip adjacent each edge and spaced from each edge a distance equal to the width of the fold and bonded thereto. The strips of cellulose acetate are at least slightly wider than the width of the fold and are preferably three or four times as wide.

The edges of the laminated strip which extend beyond the strips of cellulose acetate are then folded over the edges of the acetate strips and the assembly cut into lengths sufficiently long to cover the periphery of the slots in which they are to be placed with enough additional material for a double fold at each end across the width of the slot adjacent their open ends so as toform a backing for the slot wedges.

If desired, the strip may be cut into the right lengths prior to the folding operation.

The short lengths are then folded in U-shape across the folded edges so that the folds are on the outside of the U and the fabric on the inside.

The liners are assembled in the slots with the ends of the liners extending from the slots and the edges of the folds positioned against the ends of the core so as to hold the liners in proper assembly.

The coil windings may then be placed in the slots in any desired manner. After the windings are in place, the extending ends of the liner are each given a double fold across the width of the slots so as to lie againstthe coils or windings and slot wedges, preferably of wood, are forced into the slots against the four folds of the liner so as to tightly hold the coils and liners in place.

Other objects and advantages of this invention will become apparent as the description proceeds when taken in connection with the accompanying drawings, in which:

Figure 1 is an end view of the stator of a mo tor showing the manner in which the coils are applied;

Figure 2 is a cross-sectional view taken on line 2-2 of Figure 1 showing the coils and the slot liners, according to this invention, in place;

Figure 3 is a cross-sectional view taken on line 3-3 of Figure 2;

Figure 4 is a perspective view of the portion of a blank showing how a slot liner, according to this invention, is reenforced; and

Figure 5 is a blank showing the slot liner, according to this invention, prior to its final assembly.

Referring to the drawings, the reference numeral It indicates the stator or core of a motor or other dynamo electric machine having a plurality of laminations II as shown in Figure 2. While the core of the motor has been shown as of the laminated type, it is to be understood that the invention is also applicable to motors of any other type.

The core ill is provided with a plurality of teeth I! having widened ends l3 spaced circumferentially about the core so as to form a plurality of coil receiving slots it having narrow mouth openings and being widened towards their bottoms.

Coils or windings ii are placed in slots I I in any simple suitable manner. The coils or windings l5 are extended from the ends of one of the slots l4 and bent transversely of the slot edges so as to enter another slot spaced circumferentially from the first slot.

This causes the coils or windings l5, which are usually made of magnet wire having an enamel insulation coating to be bent rather sharply The liner selected to disclose this invention comprises a sheet of insulating paper l1, which may be treated or untreated as desired, with'a sheet of treated fabric 25 cemented thereto. The laminated sheet composed of the paper I! and the fabric 25 is old in the art and forms no part of the present invention except in combination with the reenforcing tapes of this invention which will be described in more detail hereinafter.

A large sheet of the insulating material, whether of the laminated type described above or of any other type, is cut into strips as shown in Figure 5. The width W of the strips is somewhat wider than the length (or depth) of the core III.

Two tapes l8, preferably having a tacky surface, are then secured to the paper side of the strip with the outer edges of th tape spaced from the edges of the strip a distance less than the width of the tape. The tapes 18 are made of a material having both high dielectric and mechanical strength and preferably of cellulose acetate or other cellulose derivative such as a cellulose fiber. I

The edges of the strip, which extend beyond the outer edges of the tapes ll, are then folded towards each other into a hem-like formation over the edges of the tapes l8 so as to lie in super-imposed relationship on the top of the tapes l8 as shown at IQ of Figure 4. Thewidth W of the strip and the distance Y between the edges of the strip and the outer edges of the tapes it are such that the distance between the inner edges of the folds I9 is substantially the same as the depth (or length) of the core I I.

The strips are then cut into lengths equal to the peripheral length of the slots ll plus a length of material somewhat less than four times (between three and four times) the width of the slots ll immediately behind their open ends.

The resulting liners l6 are then folded into a substantially U-shape across the folds I! with the folds on the outside of the U as shown in Figure 2.

The liners l6 are then inserted into the slots 14 in any suitable manner so that the inner edges of the folds l9 will substantially abut the ends of the core 10 about the periphery of the slots l4 and with the legs of the U extending from the open ends of the slots ll.

The coils or windings 15 are then mounted in the slots I4 in any suitable manner. One leg of the liner I6 is then bent across the width of the slots H forming a layer 20 lying against the coils l5 and reversely to form a second layer 2| lying against the first layer 20. The other leg of the liner I6 is also bent across the width of the slots ll in a similar manner to form two layers 22 and 23 lying against the lower layer 2| of the first leg.

All four layers 20, 2|, 22 and 22 are then forced tightly against the coils I5 by wooden slot wedges 24 which are held in place by the widened ends l3 of the teeth l2.

As will be noted, the fabric layer 25 is thus positioned against the coils l5 and the tapes ll extend from beneath the folds I! to a position between the paper layer I1 and the laminations ll about the periphery of the slots ll adjacent their ends.

Preferably, the width of the tapes I. is three or four times the width of the folds I! so as to present a firm support between the paper layer I! of the liner l6 and the laminatlons ll. However, this width may be less, the only limitation being that the tapes extend into the slots ll between the paper layer I1 and the laminations ll.

Thus, as can be seen, the tapes l8 provide a reenforcement having a high dielectric strength as well as mechanical strength where the coils ii are bent about sharp edges of the slots II. This will prevent the vibrations of the motor from wearing through the enamel insulation on the coils 15 where they are bent across the edges of the slots H even though the layers of the liner l8 proper should become broken. It will also prevent short-circuiting between the coils and core should a break occur in the insulation of the wires of the coils l5.

While it is preferable that the tapes It be positioned next to the metal laminations II, it is within the purview of this invention to bend the fold l8, Fig. 4 in the opposite direction using the outer edge of the tapes It as guide lines. In that case when the liners l8 are assembled the tapes l8 will be next to the coils I 5.

While I have shown the invention applied to the stator of an electric motor it is equally applicable to a motor rotor or to other electric machines such as generators.

While I have shown but a single embodiment in my invention it is to be understood that this embodiment is to be taken as illustrative only and not in a limiting sense. I do not wish to be limited to the particular structure shown and described but to include all equivalent variations thereof except as limited by the scope of the claims.

I claim:

1. A blank for use in making liners for the core slots of a dynamoelectric machine comprising, a strip of insulating material having one lineal dimension slightly greater than the length of the slots into which the liners are to be placed and a narrow reenforcing tape secured to one face of the strip adjacent each of the edges which define said one lineal dimension with the outer edges of the tapes being spaced inwardly from the edges of the strip a distance less than the width of the tape.

2. A blank for use in making a liner for the core slot-s of a dynamoelectric machine comprising, a strip of insulating material having one lineal dimension slightly greater than the length of the slot into which the liner is to be placed and a narrow reenforcing tape secured to one face of the strip adjacent each of the edges which define said one lineal dimension with the outer edges of the tapes being spaced inwardly from the edges of the strip one-fourth of the distance that said one lineal dimension is greater than the length of the slot into which the liner is to be placed, said tape being wider than the distance between the outer edges of the tape and the edges of the strip which define said one lineal dimension.

3. An insulation liner adapted to be received in the core slots of a dynamoelectric machine comprising, a sheet of insulating material in the form of a rectangle having two parallel edges folded over to form a hem-like fold facing each other along said edges, said strip being of such size that the distance between the facing edges of the folds equals the length of the slot into which the liner is to be placed and the length of the edges along the fold equals to or exceeds the peripheral length of the slots into which said liner is to be placed and a narrow reenforcing strip of high dielectric and mechanical strength adhesively bonded to said strip beneath each of said folded edges, said strips extending along the length of said folds with one edge positioned at the closed end of the folds and the other edge at a point beyond the ends of the folds.

4. A dynamoelectric machine comprising, a core having teeth on one peripheral face thereof extending peripherally about said core, said teeth having widened ends so as to form peripherally spaced slots having narrow openings extending to i the face of the core, insulation liners in each slot, each liner having an outwardly extending fold at each end extending toward and abutting the end faces of said core, a reenforcing tape secured to each end of said each liner and extending in length about the periphery of said slots, said tape lying between the fold and extending in width from the bight of said fold to a point inwardly of the ends of said slots between said liner and the walls of said slots.

5. A dynamoelectric machine comprising, a core having teeth on one peripheral face thereof extending peripherally about said core, said teeth having widened ends so as to form peripherally spaced slots having narrow openings extending to the face of the core, insulation liners in each slot, each liner having an outward fold at each end extending toward and into juxtaposition to each end face of said core and of a length substantially equal to the peripheral length of said slots plus between three and four times the width of said slots adjacent their open ends, a reenforcing tape of the same length as said liners secured beneath each folded end and extending to a point inwardly of the ends of said slots, coils in said slots and lying in said liners, one end of each liner being folded across said slots against said coils and reversely with the second fold lying against the first, the other end of each liner being folded across said slots against the folds of the first end and reversely with the second fold lying against the first.

6. A liner for core slots comprising, a strip of insulation and a narrow tape of a material having high dielectric and mechanical strength secured to one side of said strip adjacent to each of two parallel edges of said strip with the outer edges of the tapes being spaced inwardly from the edges of the strip a distance less than the width of said tape.

7. A liner for core slots comprising, a strip of insulation and a narrow tape of a material having high dielectric and mechanical strength secured to one side of said strip adjacent to each of two parallel edges of said strip with the outer edges of the tapes being spaced inwardly from the edges of the strip a distance less than the width of said strip, the free edges of said strip being folded backwardly so as to be super-imposed over said tape, so that the adjacent edges of the folds are spaced apart a distance substantially equal to the length of the slots into which the liner is to be placed.

8. A liner for core slots comprising, a strip of insulation in the form of a lamination composed of a strip of insulation material and an insulating fabric cemented thereto, said strip being of a width slightly greater than the length of the slot into which said liner is to be placed, a narrow 7 band of cellulosei awretaiiled.1 tape adherecll1 to tthe REFERENCES CITED paper side of sa s ip acent to eac of we v parallel edges thereof with the outer edges oi said i t; g g z fg are of record m the tapes being spaced inwardly of the edges of said strip a distance less than the width of said tape, 5 UNITED STATES PATENTS said strip having the free edges folded inwardly mm super-imposed relationship with said tape, "$131 g g the outer edges of said tape extending to the 1 Apple "Sept 1934 ends the and the edges 2:173I'12s Prindie Bept 19 1039 said tape extending beyond the free ends of said 10 folds.

' WIILIAM T. KIRKPATRICK 

